1. Field of the Invention
The present invention relates to a liquid crystal display module and a back light for the same. More specifically, the present invention relates to a liquid crystal display module and a back light for the same having a dust-proof structure.
2. Description of the Related Art
A display device configured to integrate a liquid crystal panel with an illumination panel to enhance a dust-proof effect of a liquid crystal display module has been disclosed in Japanese Unexamined Patent Publication No. 2003-005658 (p. 2–3, FIG. 3 and FIG. 5), for example.
The display device disclosed in the publication includes a display unit which maintains a constant space between a display panel and an illumination panel for illuminating the display panel by use of a frame body. This display unit is covered with a protection cover unit. In particular, the frame body is made of a flexible member and protrusions are integrally formed on the frame body so as to fill the space between the protection cover and the frame body.
However, this display device adopts the structure of the frame body and an illumination mode of a front light version. Accordingly, application of this display device is limited to small-sized liquid crystal display products such as a portable terminal. It is difficult to apply the display device disclosed in the publication to medium-sized liquid crystal display products such as a notebook personal computer or to large-sized liquid crystal display products such as a PC monitor or a television.
There are two options applicable to the above-mentioned medium-sized or large-sized liquid crystal display devices for achieving the dust-proof effect, which are described below.
Firstly, FIG. 1 is a cross-sectional view of a liquid crystal display module adopting a side type back light representing a conventional example. Here, only the left half of the liquid crystal display module is illustrated herein as the liquid crystal display module has a substantially symmetrical shape.
Referring to FIG. 1, a liquid crystal display module 12 of a first conventional type includes a liquid crystal panel 2, a back light mechanism 11a for providing illumination light to this liquid crystal panel 2 from backside, and a frame mechanism. Moreover, particularly, inside a lower frame 9a of a box shape, the back light mechanism 11a includes lamps 8 as light sources, a reflector 6a for reflecting illumination light from the lamps 8, an optical waveguide 7 for guiding this illumination light to the backside of the liquid crystal panel 2, and an optical sheet 5 disposed to cover part of upper ends of this optical waveguide 7 and the reflector 6a. Meanwhile, for the purpose of protection against dust or impact, the frame mechanism includes an upper frame 1, an intermediate frame 4a, and the lower frame 9a for covering the periphery and upper and lower surfaces.
The back light mechanism 11a thus configured is called a side type back light because the lamps 8 are disposed on the side (hereinafter referred to as the side type back light 11a) Meanwhile, there is also a mode (a front light mode) regarding a small and thin liquid crystal display module which is configured to supply the illumination light from a front face side of the liquid crystal panel 2. However, consideration will be made herein only for the back light mode.
Moreover, in this liquid crystal display module 12, an elastic member 3a is fixed between the rear face of the liquid crystal display module 12 and the intermediate frame. 4a to maintain air tightness between the liquid crystal panel 2 and the side type back light 11a in light of dust protection.
This elastic member 3a is formed into a rectangular cross section and besides is fixed to a projecting flat surface of the intermediate frame 4a constituting the back light 11a with a double-faced tape. That is, this elastic member 3a is fixed to the flat surface opposed to the liquid crystal panel 2 with the double-faced tape. As a result, the liquid crystal panel 2 is mounted so as to contact the elastic member 3a. 
For this reason, in a large-sized liquid crystal panel, for example, there is a risk that a gap is formed partially between the liquid crystal panel 2 and the elastic member 3a when planarity of a surface of the liquid crystal panel 2 contacting the elastic member 3a is compromised due to slight warpage. Moreover, when the liquid crystal display module 12 is used in the state placed upright on a floor surface and then tilted to some extent, the liquid crystal panel 2 comes close to the rear surface of the upper frame 1 and it becomes further prone to forming a gap between the liquid crystal panel 2 and the elastic member 3a. In this case, it is not possible to prevent intrusion of dust completely.
In the meantime, the elastic member 3a of the liquid crystal display module 12 is fixed to the rear surface of the upper frame 1 opposed to a display surface of the liquid crystal panel 2 with a double-faced tape. Moreover, a surface of the elastic member 3a opposed to the liquid crystal panel 2 comes close to the display surface of the liquid crystal panel 2. Here, since there is the gap between the liquid crystal panel 2 and the elastic member 3a, it is not possible to prevent intrusion of dust completely. Furthermore, in an attempt to reduce the gap between the liquid crystal panel 2 and the elastic member 3a as much as possible, the liquid crystal panel 2 and the elastic member 3a may completely abut on each other depending on quality of members such as the upper frame 1, and thereby puts a load on the liquid crystal panel 2. Therefore, the display performance of the liquid crystal panel 2 may be adversely affected, which may cause deterioration in display quality or yields.
Next, a liquid crystal display module of a second conventional type will be described. FIG. 2 is a cross-sectional view of a liquid crystal display module adopting a direct back light, which represents the liquid crystal display module of the second conventional type. Here, only substantially the left half of the liquid crystal display module 12 is illustrated herein as the liquid crystal display module also has a substantially symmetrical shape. Moreover, a direct back light 11b includes lamps 8 at the bottom of a reflector 6b, that is, directly below the liquid crystal panel 2. Accordingly, this is referred to as direct back light structure.
The liquid crystal display module 12 using this direct back light 11b includes the liquid crystal panel 2, the direct back light 11b, and a frame mechanism having an upper frame 1, an intermediate frame 4b, and a lower frame 9b. Inside the lower frame 9b, the direct back light 11b includes the lamps 8, and the reflector 6b for reflecting light emitted from these lamps 8 and directing the light efficiently to the liquid crystal panel 2 side through a diffuser 10 and an optical sheet 5.
In this liquid crystal display module 12,, an elastic member 3a having a rectangular cross section is fixed to a side surface of a lamp holder set 13 rendered detachable outward therefrom with a double-faced tape. Moreover, a constant gap is formed between the elastic member 3a and the intermediate frame 4b. 
This gap between the elastic member 3a and the intermediate frame 4b is necessary for preventing detachment of members, interference, scratches and the like when detaching the lamp holder set 13. However, since there is no shielding from outside space, dust may intrude from the gap and the dust may reach the rear surface of the diffuser 10 or the front surface of the optical sheet 5, thereby causing deterioration in display quality or yields.
The above-described display device disclosed in Japanese Unexamined Patent Publication No. 2003-005658 intends to enhance dust-proof effect in a small-sized display instrument such as a portable terminal. Particularly, the illumination mode in this display device is of the front light type. That is, this is the type configured to locate an illumination panel above (in front of) a display panel. In this small-sized display instrument, the dust-proof effect is enhanced by providing a frame body with protrusions. This conventional example is intended for preventing intrusion of dust between the rear surface of a sensor device such as a touch panel and the front surface of a front light (an illumination panel), and is not intended for preventing intrusion of dust inside a liquid crystal display module such as a space between the rear surface of a liquid crystal panel and an optical sheet.
Moreover, since this display device includes the flexible frame body, the display device has poor rigidity. Therefore, from the viewpoints of protection of optical members and assembly performances, such a display device is hardly applicable to middle-sized or large-sized liquid crystal products. In addition, the frame body in this display device includes a protruded portion which is integrally formed thereon. Accordingly, a long period of time and high costs are required to modify the shapes of the frame body and the protruded portion.
Furthermore, in the conventional liquid crystal display modules explained with reference to FIG. 1 and FIG. 2, there is a gap between the elastic member and a member opposed to the elastic member. Accordingly, dust may intrude and deteriorates the display quality and the yields.
The present invention has been made in consideration of the foregoing problems. It is an object of the present invention to provide a liquid crystal display module and a back light for the same, which are capable of preventing intrusion of dust and enhancing display quality, vibration resistance, and impact resistance without adversely affecting a display condition of a screen by use of an elastic member represented by silicone rubber.